Evidence Lacking on Relation Between IVF and Long-Term Risk of Breast Cancer

A long-term follow up study among Dutch women who underwent in-vitro fertilization (IVF) treatment in the Netherlands, about 25 to 30 years ago, has failed to find an association between the treatment and an increased risk of breast cancer.

The study, published in The Journal of the American Medical Association, was designed subsequent to an earlier study that was inconclusive due to limited follow up. The objective was to assess the risk in women whose hormones were being regulated for the sake of ovarian stimulation during IVF.

The IVF treatment process manipulates a woman’s hormones, particularly estradiol and progesterone levels, it has led to unproved hypothesis of the influence of IVF on breast cancer risk. With a global rise in the number of IVF procedures, this could be a potential public health concern.

More than 19,000 women who initiated IVF treatment between 1983 and 1995 (IVF group) and nearly 6000 women who started other fertility treatments between 1980 and 1995 (non-IVF group), were included in the study cohort. This OMEGA study had completed follow up in 96% of more than 25,000 women in the study by December 2013. The primary objective was to compare breast cancer risk in the IVF group with risks in the non-IVF group and the general population.

At the end of a median follow up period of 21.1 years, 839 cases of invasive breast cancer and 109 cases of in situ breast cancer were documented. The bottom line was that the risk in IVF-treated women was not very different from that in the general population (Statistical Information on Recidivism (SIR), 1.01 [95% CI, 0.93-1.09]) or in the non-IVF cohort (HR, 1.01 [95% CI, 0.86-1.19]). Importantly, the risk was significantly lower for those who underwent 7 or more IVF cycles (HR, 0.55 [95% CI, 0.39-0.77]) compare with those who underwent 1 to 2 cycles.

Additionally, the risk was not modified by the kind of fertility drugs used or the subfertility diagnosis. But a poor response to the first IVF cycle was correlated with a reduced risk of developing breast cancer.

Based on their exhaustive study, the authors conclude that they failed to find an association between IVF treatment and the long-term risk of developing breast cancer.

Reference

van den Belt-Dusebout AW, Spaan M, Lambalk CB, et al. Ovarian stimulation for in vitro fertilization and long-term risk of breast cancer. JAMA. 2016;316(3):300-312. doi:10.1001/jama.2016.9389.